Pouch-type secondary battery including electrode lead having current limiting function

Abstract

A pouch-type secondary battery includes an electrode assembly equipped with an electrode tab, an electrode lead connected to the tab, a pouch housing accommodating and sealing the electrode assembly such that the lead is exposed partly and equipped with a sealing zone at the edge thereof, a first sealant interposed between the top surface of the lead and the inner surface of the housing and a second sealant interposed between the lower surface of the lead and the inner surface of the housing. The lead includes a joint portion joined to the tab, a terminal portion exposed to the outside of the housing and a fuse portion therebetween. The fuse portion includes a separating groove separated from the sealing zone toward the joint portion and including at least a horizontal slit and a breaking portion connected to the separating groove for separating the terminal portion from the joint portion.

What is claimed is: 
     
       1. A pouch-type secondary battery comprising:
 an electrode assembly equipped with an electrode tab; 
 an electrode lead connected to the electrode tab; 
 a pouch housing accommodating and sealing the electrode assembly such that the electrode lead is exposed partly and equipped with a sealing zone at an edge thereof; 
 a first sealant interposed between a top surface of the electrode lead and an inner surface of the pouch housing and a second sealant interposed between a lower surface of the electrode lead and the inner surface of the pouch housing, 
 wherein 
 the electrode lead comprises a joint portion joined to the electrode tab, a terminal portion exposed to an outside of the pouch housing, and a fuse portion between the joint portion and the terminal portion, 
 the fuse portion comprises a separating groove separated from the sealing zone toward the joint portion and including at least a horizontal slit which is parallel to a width direction of the electrode lead and a breaking portion disposed more inwardly than the sealing zone and connected to the separating groove for separating the terminal portion from the joint portion, wherein the horizontal slit comprises a first horizontal slit relatively close to the sealing zone at a center thereof and comprises second horizontal slits relatively far from the sealing zone at both sides of the first horizontal slit, and 
 shapes of the first sealant and the second sealant are different from each other such that, when pressure inside the secondary battery is increased, stress applied to the pouch housing is in opposite directions at the top surface and the lower surface of the electrode lead so that the breaking portion breaks. 
 
     
     
       2. The pouch-type secondary battery according to  claim 1 , wherein the terminal portion of the electrode lead is completely separated from the joint portion of the electrode lead in opposite directions as the breaking portion breaks. 
     
     
       3. The pouch-type secondary battery according to  claim 1 , wherein the first sealant is formed on the electrode lead on only a first side of the horizontal slit and the second sealant is formed on the electrode lead on both the first side and a second sides of the horizontal slit. 
     
     
       4. The pouch-type secondary battery according to  claim 1 , wherein the joint portion has a larger width than a width of the terminal portion, wherein the widths are parallel to a plane defined by an electrode of the electrode assembly. 
     
     
       5. The pouch-type secondary battery according to  claim 4 , wherein the horizontal slit has a length which is the same as the width of the terminal portion. 
     
     
       6. The pouch-type secondary battery according to  claim 1 , wherein the separating groove further comprises a vertical slit at both ends of the first horizontal slit, which is perpendicular to the width direction of the electrode lead and faces the joint portion, and a vertical slit at both ends of each of the second horizontal slits, which is perpendicular to the width direction of the electrode lead and faces the terminal portion, and the breaking portion is positioned along a line extending from the vertical slit to face the terminal portion. 
     
     
       7. The pouch-type secondary battery according to  claim 1 , wherein the first sealant is formed in the form of a band crossing the top surface of the electrode lead to be adhered to the pouch housing and has a portion protruding toward each of the second horizontal slits so as to cover the top surface of the electrode lead above the second horizontal slits, and the second sealant is formed in the form of a band crossing the lower surface of the electrode lead to be adhered to the pouch housing and has protruding portions such that it can be formed on the lower surface of the electrode lead outside the vertical slit. 
     
     
       8. The pouch-type secondary battery according to  claim 5 , wherein the separating groove further comprises a vertical slit at both ends of the horizontal slit, which is perpendicular to the width direction of the electrode lead and faces the terminal portion, and the breaking portion is positioned along a line extending from the vertical slit to face the terminal portion. 
     
     
       9. The pouch-type secondary battery according to  claim 8 , wherein the first sealant is formed in the form of a band crossing the top surface of the electrode lead to be adhered to the pouch housing and has a portion protruding toward the horizontal slit so as to cover the top surface of the electrode lead above the horizontal slit, and the second sealant is formed in the form of a band crossing the lower surface of the electrode lead to be adhered to the pouch housing and has protruding portions such that it can be formed on the lower surface of the electrode lead outside the vertical slit. 
     
     
       10. The pouch-type secondary battery according to  claim 1 , wherein the electrode lead has a shape of an inverted T, wherein a leg portion of the T protrudes from inside the sealing zone to outside the pouch housing and a head portion of the T is formed more inwardly than the sealing zone. 
     
     
       11. The pouch-type secondary battery according to  claim 1 , wherein a notch is formed in the breaking portion. 
     
     
       12. The pouch-type secondary battery according to  claim 11 , wherein the notch is formed in at least one of the top surface and the lower surface of the electrode lead. 
     
     
       13. The pouch-type secondary battery according to  claim 1 , wherein the breaking portion has one or more through-holes formed therein. 
     
     
       14. The pouch-type secondary battery according to  claim 1 , wherein the electrode lead is at least one of a cathode lead and an anode lead. 
     
     
       15. The pouch-type secondary battery according to  claim 1 , wherein a front end of the breaking portion is cut partly. 
     
     
       16. The pouch-type secondary battery according to  claim 15 , wherein the separating groove further comprises a connecting portion at the center of the horizontal slit. 
     
     
       17. The pouch-type secondary battery according to  claim 16 , wherein a notch is formed in the connecting portion. 
     
     
       18. The pouch-type secondary battery according to  claim 17 , wherein the notch is formed in at least one of the top surface and the lower surface of the electrode lead. 
     
     
       19. The pouch-type secondary battery according to  claim 16 , wherein the connecting portion has one or more through-holes formed therein.